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Chapter 8: Cell Reproduction. Section 1: Chromosomes Section 2: Cell Division Section 3: Meiosis. What are chromosomes?. Rod shaped structures inside the nucleus of Eukaryotic cells Made of DNA and proteins Contain the genes that make you, you!
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Chapter 8: Cell Reproduction Section 1: Chromosomes Section 2: Cell Division Section 3: Meiosis
What are chromosomes? • Rod shaped structures inside the nucleus of Eukaryotic cells • Made of DNA and proteins • Contain the genes that make you, you! • Shape of the chromosome is maintained by histones
Chromosome Structure • 3 forms of a chromosome • Chromatin – ball of yarn • Chromatid – half of an x, sometimes bent • Chromosome – X • Center of X is called a centromere
Chromosome Types • Sex Chromosomes • Determine the sex of the organism • Males XY • Females XX • 2 out of 46 in the human cell • Autosomes • All the other chromosomes • 44 out of 46 in the human cell
Section 1 Chromosomes Chapter 8 Sex Chromosomes and Autosomes Click below to watch the Visual Concept. Visual Concept
What are Homologous Chromosomes? • Also called homologues • 2 copies of the chromosome • One from Mom; One from Dad • Have the same size • Have the same shape • Have the same information (genes)
Two Types of Cells • Diploid • Cells that have chromosomes in pairs • Symbol 2n • Somatic cells or body cells are like this • Humans diploid number is 46. • Haploid • Cells that do not have chromosomes in pairs • Symbol 1n • Gametes are like this • Sex cells • Sperm and egg cells • Humans haploid number is 23.
Section 2 Cell Division Chapter 8 Cell Division in Prokaryotes, continued • Binary fissionis the process of cell division in prokaryotes.
Two types of Reproduction • Asexual Reproduction • Production of offspring from one parent • Mitosis • Sexual Reproduction • Production of offspring from 2 parents • Meiosis
The process of asexual reproduction begins after a sperm fertilizes an egg.
Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cell that reproduce by asexual reproduction reproduce constantly.
Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm • Interphase • Prophase • Metaphase • Anaphase • Telophase & Cytokinesis
Interphaseoccurs before mitosis begins • 3 phases • G1 – cell is growing • S – DNA is being copied • G2 – cell is preparing for mitosis Nuclear Membrane And nucleolus are visible CHROMATIN! CELL MEMBRANE Nucleus Cytoplasm
Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Nuclear membrane & nucleolus disappear by end of prophase Prophase 1st step in Mitosis • Mitosis begins (cell begins to divide) • Chromosomes are visible • Centrioles(or poles) appear and begin to move to opposite end of the cell. • Spindle fibers form between the poles. Centrioles Sister chromatids Spindle fibers
Prophase Plant Cell Animal Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase 2nd step in Mitosis • Chromosomes attach to the spindle fibers at the centromere CHROMOSOME Centrioles Spindle fibers
Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase 3rdstep in Mitosis • Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell. Centrioles Spindle fibers
Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Nuclear membrane & nucleolus are visible by end of telophase Telophase4th step in Mitosis • Two new nuclei form. • Chromosomes appear as chromatin (threads rather than rods). • Mitosis ends. Overlaps with cytokinesis! Nuclei Nuclei Chromatin
Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesisoccurs after mitosis • Division of the cytoplasm • Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes. • Animal cells – form a cleavage furrow • Plant cells – form a cell plate, which becomes the cell wall.
IPMATC REMEMBER! • Interphase • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis IPrayMore AtThe Church
MitosisAnimation http://www.cellsalive.com/mitosis.htm
Section 2 Cell Division Chapter 8 Control of Cell Division • Cell division in eukaryotes is controlled by many proteins. • Control occurs at three main checkpoints. • G1 checkpoint – check to see whether the cell is healthy and is large enough to divide • G2 checkpoint – check to make sure DNA is copied correctly • Mitosis checkpoint – if cell divided correctly, then signals are made to exit mitosis
Section 2 Cell Division Chapter 8 Control of the Cell Cycle Click below to watch the Visual Concept. Visual Concept
Section 2 Cell Division Chapter 8 Control of Cell Division, continued • When Control is Lost: Cancer • Cancer is uncontrolled growth of cells • Cancer may result if cells do not respond to control mechanisms. • Can be caused by mutations in DNA
Section 3 Meiosis Chapter 8 Formation of Haploid Cells • Meiosisis a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell. • Start with 46 and end with 23 • Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis. • Done by germ cells • Meiosis produces haploid gametes. • Is considered sexual reproduction • Creates genetic diversity • Two divisions
Section 3 Meiosis Chapter 8 Meiosis I • Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I. • Crossing-over, which is when portions of homologous chromosomes exchange genetics material, occurs during prophase I and results in genetic recombination.
Prophase I • Homologous chromosomes (paired chromosomes) become visible • Nuclear membrane and nucleolus disappear • Spindle fiber starts to appear • Crossing over occurs – portions of the chromatid break off and attach to other homologous chromosome
Section 3 Meiosis Chapter 8 Tetrads and Crossing-over of Genetic Material Click below to watch the Visual Concept. Visual Concept
Metaphase 1 • Homologous chromosomes (tetrads) line up at the equator and connect to spindle fibers at their centromeres
Anaphase 1 • Homologous chromosomes split and individual chromosomes move to poles • They assort independently of one another- independent assortment
Telophase 1and Cytokinesis 1 • There are 2 new cells at this point • Each new cell has half the number of chromosomes as the parent germ cell • So they are now haploid
Meiosis 2 • Has prophase II, metaphase II, anaphase II and telophase II • Exactly like mitosis • Four new haploid cells result • Four gametes • Depends on whether it is an animal or a plant cell
Section 3 Meiosis Chapter 8
Gametogenesis – making of gametes • Spermatogenesis • Making of sperm cells • Meiosis will result in 4 mature sperm cells or spermatozoa • Oogenesis • Making of mature egg cells, or ova • Meiosis will result in 1 mature egg cell and 3 polar bodies that die